A new psychophysiological measurement strategy will be assessed in human neonates. The proposed research will focus on evaluating the relationship between central nervous system (CNS) dysfunction, causal in many forms of behavior disorders, and autonomic nervous system (ANS) activity. The research will evalate the hypothesis that rhythmic heart rate patterns, specifically respiratory-sinus arrhythmia, reflect neural influences and will be sensitive to cortical pathologies. The specific objective of the proposed research is to identify CNS dysfunction in neonates through non-invasive monitoring of heart rate and respiration. In preliminary research spectral analysis techniques have been developed which have been successful in identifying and quantifying a component of heart rate variability which covaries with vagal tone (V). In a pilot study with neonates, V was related to general CNS status. The proposed research is an attempt to evaluate the sensitivity of V as an assessment index of known pathophysiological states in brain-damaged infants and to related measures of V at birth to duration of hospitalization and outcome. The techniques tested in the proposed research may evolve into an assessment technique sensitive to subtle individual differences in CNS functioning and predictive of future behavior.